View Full Version : Night time penumbra?

10-29-2004, 10:13 AM
I've read that here on earth we have a .5 degree prenumbra... So what is one caused by a full moon on a clear night?

10-29-2004, 11:17 AM
Do you mean the ring around a full moon? I don't think that's called a penumbra.

Think of a penumbra as a fuzzy shadow, to put it in terms a 3Der understands. ;)

From Websters

pe·num·bra ( P ) Pronunciation Key (p-nmbr)
n. pl. pe·num·brae (-br) or pe·num·bras
A partial shadow, as in an eclipse, between regions of complete shadow and complete illumination. See Synonyms at shade.
The grayish outer part of a sunspot.
An area in which something exists to a lesser or uncertain degree: “The First Amendment has a penumbra where privacy is protected from governmental intrusion” (Joseph A. Califano, Jr.).
An outlying surrounding region; a periphery: “Downtown Chicago and its penumbra also stand rejuvenated” (John McCormick).

10-29-2004, 12:20 PM
Thanx Matt... No, not the moon. I think I am saying this correctly?

Prenumbra - The Fuzzy shadow occuring on objects from the global illumination of light bouncing off everything. I was wondering if their is one, which I guess their is at night. I read the tutorial on spinning lights and it was saying to angle your lights a .25 degrees to duplicate the earth's prenumbra.